Multiple drops interacting on swelling fibers

The Plateau-Rayleigh instability has been extensively described over the last centuries. When a fiber is coated with a thin liquid film, this film can destabilize into multiple droplets. Many fibers such as cellulose, wood or polymer fibers may swell when interacting with a favorable solvent. In this talk, I will show how the Plateau-Rayleigh instability can be affected by the swelling of the fiber. Generally, the curvature of a fiber prevents the total spreading of a drop even if the fluid is fully wetting the fiber. On a swelling fiber, a drop locally penetrates and swells the fiber thus moving further through the polymer network. If two drops are placed close enough to each other on the same fiber, they may interact via the swollen polymer network leading to different spontaneous movements. The drops may drift apart or in some cases attract each other or even coalesce in a counterintuitive manner. In this talk, by making use of our previous work on the absorption of a single drop on a fiber, we attempt to rationalize the dynamics of two or more interacting droplets on a fiber through controlled experiments and simple models.